Any advice will be greatly appreciated on this one, I have two cards to choose from for a new rig im building.

In your opinion which of the two cards would be worth sticking with?

WinFast PX8800 GTS 640mb

or

XFX 9600gt 512mc

I'd keep the GTS.

Performance is a push, keep the 9600 GT because it's an XFX.

Looking at tom's charts, with overall fps, it does not have the 9600gt. So, what I did was I looked at the 3850, and the 8800gt.

The 3850 is about the same as an 8800gs, which is a little less than the 9600gt. The 8800gt is a little more than the 9600gt. So the 9600gt would be about right in between the 3850 and the 8800gt. And that's where the 8800gts 640 is.

So really, they're about the same. Maybe keep the gts, because it has more memory which might help later. Or maybe pick the one that is the quietest/coolest.

I don't know why, but I think I'd like the 9600gt better.

Aren't you confusing the 640mb GTS with the 512 GTS?
*Checks*

Its the 640mb version

I would keep the 8800gts. It can easily push a little harder especially overclocked. Not to mention better AA performance because of more bandwidth.

Sell both, and upgrade to a much better card for your new rig.

Keep the GTS

Actually, that might not be a bad idea. You might be able to then afford an ati card or another nvidia card.

IMO, I would stick with the 9600gt since it is a newer tech and it works perfectly fine for me.
I don't know the tech specs for comparison, but i'm sure both are quite close to one another. however, i do know that two 9600gt's in sli will kick a 9800 series in the a$$.

Either way, they are both decent cards.